1. Field
The present disclosure relates to a method and apparatus for decolorization of reactive anthraquinone dye-containing wastewater using photocatalytic oxidation. More particularly, the present disclosure relates to a method and apparatus for decolorization of reactive anthraquinone dye-containing wastewater using photocatalytic oxidation, which include inducing high-efficiency photocatalytic oxidation under a controlled salt concentration and pH of wastewater to perform effective decolorization of reactive anthraquinone dye-containing wastewater.
2. Description of the Related Art
Fiber dyeing industry is so-called highly industrial water-consuming industry requiring industrial water for substantially all of the processing operations, and thus is characterized by discharge of a large amount of water contaminants. Particularly, wastewater from fiber dyeing industry has a dark color due to the remaining dye discharged from a dyeing process, and thus incurs the enmity of the people in terms of aesthetics. Moreover, it is reported in the field of water science that such wastewater interrupts the sunlight, thereby adversely affecting the growth of aquatic plants. Therefore, there is a need for developing eco-friendly highly efficient technology of decolorizing wastewater discharged from a dyeing process.
Reactive dyes have been used most frequently all over the word, due to the production of high-quality fibers and various demands, and thus are in a rapid increase in use. In addition, since reactive dyes have diverse and clear colors and are handled with ease, they are one of the dyes used widely in recent textile industries. Among such reactive dyes, reactive anthraquinone dyes come close to azo dyes in use and are increasingly in demand.
It is known that reactive anthraquinone dyes are materials having a relatively high molecular weight (500-1000 g/mol), and have high solubility so that they are hardly removed by adsorption. It is also known that reactive anthraquinone dyes are hardly degradable materials so that they are not amenable to decolorization using a typical sewage treatment process (e.g. active sludge process). In the case of wastewater containing such reactive dyes, the dyes used for a dyeing process are not adhered to fibers but discharged in an amount as high as about 50% thereof, resulting in a dark colored wastewater. For this reason, it is the most severe environmental problem to decolorize reactive anthraquinone dye-containing wastewater in which the residual salt is still present at a high concentration. Therefore, in order to meet stringent environmental regulation, there is an imminent need for more special and cost-efficient technologies as compared to currently available wastewater treatment technologies in the field of textile industries.
Meanwhile, many studies have been conducted about decomposition of toxic and hardly degradable materials through photocatalytic oxidation. As processes for treating dye-containing textile wastewaters through oxidation, Korean Patent Application Publication Nos. 2001-91796, 2003-77865 and 2004-84586, and US Patent Application Publication No. 2005-115004 disclose oxidation processes using fenton reagents, plasma, ozone, or the like. In addition, as processes for treating dye-containing textile wastewater through photocatalytic oxidation, Korean Patent Application Publication No. 2001-8364 and Japanese Patent Application Publication No. 2001-205100 disclose processes using fixed titanium dioxide as a typical photocatalyst, processes for increasing efficiency of dye-containing wastewater treatment as a function of titanium dioxide sizes, or the like.
However, most studies reported heretofore about treatment of reactive anthraquinone dye-containing wastewater have focused on decolorization carried out after diluting highly concentrated wastewater to reduce the salt concentration to a low level. Therefore, such decolorization methods may not be practically applicable due to its low cost efficiency.